Ultimately, the observations lead to questions, or
hypotheses, that are tested in experiments, the results
of which add to or change current clinical practice, or
feed back into the cycle for another iteration of testing.

Importantly, because the cycle is iterative, it is constantly
building on prior knowledge.

Figure 8 depicts the continuum of biomedical research. ;e
cycle can be divided into several discrete stages of research,
and a brief description of each follows.

Discovery

In the discovery phase of research, hypotheses generated
from observations with medical relevance, are tested in
experiments performed using models, ranging from single
cells to whole animals, that mimic healthy and disease
conditions (see sidebar on Research Models, p. 34). In
clinical research, these models are derived from patients.
Cancer research uses models that mimic speci;c aspects
of cancer or types of cancer—for example, increased cell
growth or pancreatic cancer, respectively.